The present invention relates to a digital display device of a vehicle used for providing a digital display of information such as vehicle speed or the like.
The conventional display devices of vehicles in general use are of the pointer display type. As for example in a speedometer, it is necessarily requested under regulations to provide a vehicle speed warning device by arranging a yellow zone on the dial at a portion, for instance, indicating speeds over 100 km/h or by installing a housed contact for detecting excess speed of over 100 km/h to ring a warning chime in order to warn the driver that the vehicle speed then exceeds said certain limit, for instance, 100 km/h.
Recently the digital type display devices are increasingly used on vehicles. Accordingly in case such a digital display device is used as the vehicle speedometer, it is necessary to provide a warning display to invite attention that the vehicle speed exceeds a certain limit such as 100 km/h or to operate an excess speed warning device just the same as a conventional analog type mechanical speedometer.
It is also conventional practice to automatically lock the door or to release the exhaust gas recirculation system when the vehicle speed reaches at a certain value.
In the case of a speedometer of the digital display type, for providing the warning of excess speed or to control other vehicle mounted electric or electronic devices as mentioned above, it is not possible simply to arrange the yellow zone on the dial as in the case of the pointer display meter or to arrange a contact operated in a ON-OFF manner by the pointer and hence it is required to provide a vehicle speed detecting circuit for generating a control signal at a predetermined vehicle speed. This has the disadvantage that the circuit arrangement is complicated.